The invention relates to the fabrication of polymer film covered structural members used in residential and commercial architecture and structural members preferably used in the manufacture of windows and doors and to materials used for such members. More particularly, the invention relates to an improved composite structural member having superior properties, that can be used as a direct replacement for structural components made of wood or metal and can be joined to form strong structures. The structural members of the invention can comprise film covered sized covered lumber replacements and structural components with complex shapes such as rails, jambs, stiles, sills, tracks, stop sash and trim elements such as grid cove, bead, quarter round, etc.
Conventional window and door manufacture utilize structural members made commonly from hard and soft wood members, extruded thermoplastic and extruded metal, typically aluminum, components. Residential windows and doors are often manufactured from a number of specially shaped milled wood products that are assembled with glass sheets to form typically double hung or casement windows and sliding or hinged door units. Wood windows and doors while structurally sound and well adapted for use in many residential installations, require painting and other routine maintenance and can have problems under certain circumstances caused by insect or fungal attack and by other deterioration of wood components. Wooden windows also suffer from cost problems related to the availability of suitable wood for construction. Clear wood and related wood products are becoming more scarce and costs have increased rapidly as demand increases.
Metal windows and doors have been introduced into the marketplace. Such metal windows and doors are often made from extruded aluminum parts that when combined with glass, rubber and thermoplastic curable sealant materials form utility components. Metal windows typically suffer from the drawback that they tend to be energy inefficient and tend to transfer substantial quantities of heat from a heated exterior to a cold environment.
Extruded thermoplastic materials have been used in the manufacture of window and door components. Typically, non-structural seals, edging, grill and coatings have been manufactured from filled and unfilled thermoplastic materials. Further, thermoplastic polyvinylchloride materials have been combined with wooden structural members in the manufacturing of PERMASHIELD(copyright) brand windows manufactured by Andersen Corporation for many years. The technology for forming the PERMASHIELD(copyright) windows is disclosed in Zanini, U.S. Pat. Nos. 2,926,729 and 3,432,883. In the manufacture of the PERMASHIELD(copyright) brand windows, a polyvinylchloride envelope or coating is extruded around the wooden member as it passes through an extrusion die. Such covered members are commonly used as structural components in forming the window frame or double hung or casement units. In the typical Zanini structure the envelope is not adhered to the internal member. Structural integrity is maintained by corner welding the vinyl envelopes.
Laminated films have been formed over a variety of substrates such as those disclosed in Schock, U.S. Pat. No. 3,544,669 which discloses forming a thermoplastic laminate over a wood core by passing a wood member through an extrusion die and extruding a first adhesive coating followed by a thermoplastic film coating which is adhered to the wood member. Cooley et al., U.S. Pat. No. 4,295,910 teach vinyl film/cellulosic laminates such as a film coated particle board. The film is adhesively bonded to the particle board material. Lastly, Hewitt, U.S. Pat. No. 4,481,701 teaches a plastic profile member having an exterior laminate coating or cladding.
Significant advances have been made in articles and processes combining polymer resins such as polyvinylchloride resins and wood fiber materials in the manufacture of pellets, structural members and hollow profiles for residential and industrial window and door manufacture. U.S. Pat. Nos. 5,406,768, 5,441,801, 5,486,553, 5,497,594 and 5,539,027 disclose various aspects of an improved technology involving combining polyvinylchloride and wood fiber to make composite materials for use in structural components of windows and doors. These materials achieve a substantial Young""s modulus that can substantially exceed 500,000 psi, possess significant tensile strength, compressive strength, a coefficient of thermal expansion that matches a number of wood components, possess a resistance to insect attack, rot and deterioration, and is easy to work, shape and can be used as a direct substitute for wood materials.